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Basic I/O Unit Instructions Section 3-22
Flags
Precautions The Equals Flag will turn ON if the reading operation is completed normally.
The Equals Flag will turn OFF if the reading operation cannot be completed
normally due to the Special I/O Unit or CPU Bus Unit being busy.
Whenever any of the following occur, an error will occur and the Error Flag will
turn ON.
• The number of words to transfer (S) is outside the range of 0001 to 0080
(hex).
• The unit number (S) is outside the range of 0000 to 005F hex or 8000 to
800F hex.
• A Special I/O Unit or CPU Bus Unit not affected by IORD(222) is desig-
nated.
• A Special I/O Unit with a setting error or an error is designated.
• A CPU Bus Unit with a setting error or error is designated.
When IORD(222) is executed, the execution results are reflected in the condi-
tion flags. In particular, the Equals Flag turns ON when reading is completed.
Input the condition flags such as the Equals Flag with output branching from
the same input conditions as the IORD(222) instruction.
If the Special I/O Unit or CPU Bus Unit is busy, the reading operation will not
be executed. Use the Equals Flag to create a self-maintaining program, as
shown below, so that IORD(222) will be executed with each cycle until the
reading operation is executed.
When the input condition is met, self maintenance is performed by output A
and IORD(222) is executed with each cycle until the Equals Flag turns ON.
When the reading is completed and the Equals Flag turns ON, output B turns
ON and the self maintenance is cleared.
Name Label Operation
Error Flag ER ON if the number of words to transfer (S) is outside the
range of 0001 to 0080 hex.
ON if the unit number (S) is outside the range of 0000 to
005F hex or 8000 to 800F hex.
ON if a Special I/O Unit or CPU Bus Unit not affected by
IORD(222) is designated.
ON if a Special I/O Unit with a setting error or an error is
designated.
ON if a CPU Bus Unit with a setting error or an error is
designated.
OFF in all other cases.
Equals Flag = ON if reading operation is completed normally.
OFF if reading operation is not completed normally.
B
IORD
C
S
=
B
D
A
A
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